有的時候在使用textView的時候需要設置一些placeholder， 但是發(fā)現(xiàn)textView并沒有類似textField的placeholder屬性，那么要想實現(xiàn)類似textField的placeholder效果需要自己自定義一個textView，
代碼如下
定義一個全局的placeholderLabel，用來顯示placeholder
- (instancetype)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if(self) {
self.backgroundColor= [UIColor clearColor];
UILabel *placeholderLabel = [[UILabel alloc]init];//添加一個占位label
placeholderLabel.backgroundColor= [UIColor clearColor];
placeholderLabel.numberOfLines=0; //設置可以輸入多行文字時可以自動換行
[self addSubview:placeholderLabel];
self.placeholderLabel= placeholderLabel; //賦值保存
self.placeholderColor= [UIColor lightGrayColor]; //設置占位文字默認顏色
self.placeholderLabel.font= [UIFont systemFontOfSize:15]; //設置默認的字體
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:self]; //通知:監(jiān)聽文字的改變
}
return self;
}
- (void)textDidChange
{
//hasText 輸入文字就是yes
self.placeholderLabel.hidden =? self.hasText;
}
- (void)layoutSubviews
{
[super layoutSubviews];
self.placeholderLabel.y = 8;
self.placeholderLabel.x=5;//設置 UILabel 的 x 值
self.placeholderLabel.width=self.width-self.placeholderLabel.x*2.0; //設置 UILabel 的 x
//根據(jù)文字計算高度
CGSize maxSize =CGSizeMake(self.placeholderLabel.width,MAXFLOAT);
self.placeholderLabel.height= [self.placeholder boundingRectWithSize:maxSize options:NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName : self.placeholderLabel.font} context:nil].size.height;
}
- (void)setPlaceholder:(NSString *)placeholder
{
_placeholder = [placeholder copy];
self.placeholderLabel.text = placeholder;
//重新計算子控件frame
[self setNeedsLayout];
}
- (void)setPlaceholderFont:(UIFont *)placeholderFont
{
_placeholderFont = placeholderFont;
self.placeholderLabel.font = _placeholderFont;
}
- (void)setPlaceholderColor:(UIColor *)placeholderColor
{
_placeholderColor = placeholderColor;
//設置顏色
self.placeholderLabel.textColor= placeholderColor;
}
//重寫這個set方法保持font一致
- (void)setFont:(UIFont*)font {
[super setFont:font];
self.placeholderLabel.font= font;
//重新計算子控件frame
[self setNeedsLayout];
}
- (void)setText:(NSString*)text{
[super setText:text];
[self textDidChange]; //這里調(diào)用的就是 UITextViewTextDidChangeNotification 通知的回調(diào)
}
- (void)setAttributedText:(NSAttributedString*)attributedText {
[super setAttributedText:attributedText];
[self textDidChange]; //這里調(diào)用的就是UITextViewTextDidChangeNotification 通知的回調(diào)
}
- (void)dealloc{
[[NSNotificationCenter defaultCenter]removeObserver:UITextViewTextDidChangeNotification];
}
demo下載地址：http://download.csdn.net/detail/qq_31927183/9553359
github：https://github.com/lwy121810/WYPlaceholderTextView
